Method for forming conformal nitrided, oxidized, or carbonized dielectric film by atomic layer deposition

ABSTRACT

A method for forming a film on a patterned surface of a substrate by atomic layer deposition (ALD) processing includes: adsorbing onto a patterned surface a first precursor containing silicon or metal in its molecule; adsorbing onto the first-precursor-adsorbed surface a second precursor containing no silicon or metal in its molecule; exposing the second-precursor-adsorbed surface to an excited reactant to oxidize, nitride, or carbonize the precursors adsorbed on the surface of the substrate; and repeating the above cycle to form a film on the patterned surface of the substrate.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention generally relates to a method for forming a conformal nitrided, oxidized, or carbonized dielectric film by atomic layer deposition (ALD).

Description of the Related Art

As a method for depositing an insulation film on a substrate by ALD, substitution reaction by thermal reaction, plasma reaction, or remote plasma reaction is generally utilized. However, depending on the type of deposited film and the type of starting material, a problem may occur in that film quality is degraded because reaction in grooves of a recess pattern becomes insufficient, or secondary reaction such as physical adsorption interferes with reaction, or the like. In order to resolve the above problems, raising a process temperature and conducting post-process treatment are considered to be the most effective and have been widely conducted.

The problems of the above solutions are that when a limitation is imposed on temperature, raising the process temperature may not be acceptable, and when the post-process treatment is conducted, the total duration is prolonged, and modification reaction occurs only in a surface of a film. For example, for improving film quality in grooves by controlling temperature, the process temperature often exceeds 400° C., and also the post-process temperature often exceeds 400° C., and therefore, if the process requires a process temperature lower than 400° C., it is difficult to apply the process temperature control and the post-process treatment. In view of the above, in order to improve film quality in grooves by modifying reaction between a process material and a reactant, evaluating new materials, studying the dependency of reactant gas type, and researching comprehensive reactant reactions have been conducted. However, these attempts have not resolved the problems and have not fundamentally improved film quality in grooves.

Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.

SUMMARY OF THE INVENTION

The present inventors conducted research on the process sequence dependency of the quality of film in grooves and discovered that by reacting a precursor multiple times in one cycle using a reactant, and by changing reactants and reacting a precursor multiple times in one cycle, the film quality in grooves can be improved. For example, wet etch rate of the film in grooves was improved from 5 times that of the film on a top surface to 1.2 times that of the film on a top surface. However, growth rate of the film per cycle of ALD became significantly low, which became a problem. In view of the above, in an embodiment of the present invention, a method for forming a film on a patterned surface of a substrate by atomic layer deposition (ALD) processing comprises: (i) adsorbing onto the patterned surface a non-excited gas of a first precursor containing silicon or metal in its molecule; and then (ii) adsorbing onto the first-precursor-adsorbed surface a non-excited gas of a second precursor containing no silicon or metal in its molecule, thereby rendering the substrate surface more easily oxidized, nitrided, or carbonized. In the next step, the second-precursor-adsorbed surface is exposed to an excited gas of a reactant in the reaction space to oxidize, nitride, or carbonize the precursors adsorbed on the surface. The above cycle is repeated to form a film on the patterned surface of the substrate. Accordingly, the quality, uniformity, and conformality of film in grooves can be improved while maintaining appropriate growth rate.

For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Further aspects, features and advantages of this invention will become apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.

FIG. 1 shows a schematic process sequence of PEALD in one cycle according to a comparative example (the size of each column does not represent duration of each process).

FIG. 2 shows a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a step illustrated in a column represents an ON state whereas no step illustrated in a column represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 3 shows a schematic process sequence of PEALD in one cycle according to another embodiment of the present invention wherein a step illustrated in a column represents an ON state whereas no step illustrated in a column represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 4 shows a schematic process sequence of PEALD in one cycle according to still another embodiment of the present invention wherein a step illustrated in a column represents an ON state whereas no step illustrated in a column represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 5 shows a schematic process sequence of PEALD in one cycle according to yet another embodiment of the present invention wherein a step illustrated in a column represents an ON state whereas no step illustrated in a column represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 6 is a schematic representation of a PEALD apparatus for depositing a dielectric layer usable for an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid and may be constituted by a single gas or a mixture of gases. Likewise, an article “a” or “an” refers to a species or a genus including multiple species. In this disclosure, a process gas introduced to a reaction chamber through a showerhead may be comprised of, consist essentially of, or consist of a first precursor containing silicon or metal, a second precursor containing no silicon or metal, and a reactant gas. In some embodiments, the term “precursor” refers generally to a compound that participates in the chemical reaction that produces another compound, and particularly to a compound that constitutes a film matrix or a main skeleton of a film, whereas the term “reactant” refers to a gas that activates a precursor, modifies a precursor, or catalyzes a reaction of a precursor. The reactant includes a gas for oxidizing, nitriding, or carbonizing the precursors when RF power is applied to the reactant gas. The first precursor, the second precursor, and the reactant gas may be different from each other or mutually exclusive in terms of gas types, i.e., there is no overlap of gas types among these categories. The precursor and the reactant gas can be introduced separately or simultaneously to a reaction space. The precursor can be introduced with a carrier gas such as a rare gas, and additionally, a dilution gas such as a rare gas can also be introduced to the reaction space. A gas other than the process gas, i.e., a gas introduced without passing through the showerhead, may be used for, e.g., sealing the reaction space, which includes a seal gas such as a rare gas. In some embodiments, “film” refers to a layer continuously extending in a direction perpendicular to a thickness direction substantially without pinholes to cover an entire target or concerned surface, or simply a layer covering a target or concerned surface. In some embodiments, “layer” refers to a structure having a certain thickness formed on a surface or a synonym of film or a non-film structure. A film or layer may be constituted by a discrete single film or layer having certain characteristics or multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers. Further, in this disclosure, any two numbers of a variable can constitute a workable range of the variable as the workable range can be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments.

In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.

In the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation.

In all of the disclosed embodiments, any element used in an embodiment can be replaced with any elements equivalent thereto, including those explicitly, necessarily, or inherently disclosed herein, for the intended purposes. Further, the present invention can equally be applied to apparatuses and methods.

An embodiment provides a method for forming a film on a patterned surface of a substrate by atomic layer deposition (ALD) processing wherein the surface is patterned with a recess having side walls and a bottom. The method comprises: (i) adsorbing a non-excited gas of a first precursor onto a patterned surface of a substrate in a reaction space, said first precursor containing silicon or metal in its molecule; (ii) adsorbing a non-excited gas of a second precursor onto the first-precursor-adsorbed surface of the substrate in the reaction space, said second precursor containing no silicon or metal in its molecule; (iii) exposing the second-precursor-adsorbed surface of the substrate to an excited gas of a reactant in the reaction space to oxidize, nitride, or carbonize the precursors adsorbed on the surface of the substrate, said reactant having a smaller molecular size than the second precursor and being reactive to both the first and second precursors in step (iii); and (iv) repeating steps (i) to (iii) to form a film on the patterned surface of the substrate. After adsorbing the first precursor containing silicon or metal on the substrate, by adsorbing the second precursor containing no silicon or metal immediately on top of the first-precursor adsorbed surface so as to form Si—O—X, Si—N—X, or Si—C—X (X represents an element other than silicon and metal in the precursors), thereby promoting oxidizing, nitriding, or carbonizing the precursors adsorbed on the surface of the substrate when exposing the second-precursor-adsorbed surface of the substrate to an excited gas of a reactant. In some embodiments, the non-metal element in the second precursor includes a metalloid such as boron. The second precursor has a higher molecular size than the reactant and is typically in liquid form at room temperature, which requires vaporization for feeding it to the reaction space using a carrier gas. In contrast, the reactant has a smaller molecular size than the precursor and is typically in gaseous form. The first precursor is also typically in liquid form at room temperature, which requires vaporization for feeding it to the reaction space using a carrier gas.

In some embodiments, the second precursor is at least one compound selected from the group consisting of C_(x)H_(y)O_(z), C_(x)O_(y), and N_(x)C_(y)O_(z) (x, y, and z are integers), and the reactant is at least one gas selected from the group consisting of O₂, O₃, CO₂, H₂O, and N₂O, whereby the excited reactant oxidizes the precursors adsorbed on the surface of the substrate. For example, the second reactant may be an ether compound such as diethylether and dimethylether.

In some embodiments, the second precursor is at least one compound selected from the group consisting of C_(x)N_(y)H_(z) and N_(x)H_(y) (x, y, and z are integers), and the reactant is at least one gas selected from the group consisting of N₂, N₂ and H₂, NH₃, N_(x)H_(y), and N_(x)H_(y)C_(z) (x, y, and z are integers), whereby the excited reactant nitrides the precursors adsorbed on the surface of the substrate. For example, the second reactant may be an amine compound such as diethylamine and dimethylamine.

In some embodiments, the second precursor is at least one compound selected from the group consisting of C_(x)H_(y) and C_(x)N_(y)H_(z) (x, y, and z are integers), and the reactant is at least one gas selected from the group consisting of H₂, N₂, Ar, and He, whereby the excited reactant carbonizes the precursors adsorbed on the surface of the substrate.

In some embodiments, the first precursor is a halide compound such as dichlorodiethylsilane, dichlorodimethylsilane, dichlorotetramethyldisilazane, dichlorotetraethyldisilazane, dichloroethylsilane, dichloromethylsilane, diiodomethylsilane, diiodoethylsilane. In some embodiments, the first precursor is an aminosilane compound such as bis(diethylamino)silane and bis(dimethylamino)silane. In some embodiments, the first precursor contains a metal selected from the group consisting of Ti, Zr, Al, and Mn, such as tris(dimethylamino)titanium, tris(diethylamino)titanium, dimethylaluminium-isopropoxide, diethylaluminium-isopropoxide, and aluminium diisopropoxide, wherein after adsorbing the first precursor, by adsorbing the second precursor containing no silicon or metal immediately on top of the first-precursor adsorbed surface so as to form M-O—X, M-N—X, or M-C—X (M represents a metal, and X represents an element other than silicon and metal in the precursors), thereby promoting oxidizing, nitriding, or carbonizing the precursors adsorbed on the surface of the substrate when exposing the second-precursor-adsorbed surface of the substrate to an excited gas of a reactant. In some embodiments, the first and second precursors are organic compounds.

In some embodiments, the adsorbed weight of the second precursor in step (ii) is equivalent to or higher (e.g., about 1.5 times higher, but typically no more than 10 times, 50 times, or 100 times higher) than the adsorbed weight of the first precursor in step (i), whereby refractive index of a resultant film can be increased.

In some embodiments, the reactant is excited by heat and/or a plasma in step (iii). In some embodiments, the reactant is excited by a plasma generated by applying RF power to the reaction space. In some embodiments, the reactant is continuously supplied to the reaction space throughout steps (i) to (iii), and RF power is applied in step (iii). In the above, “continuously” refers to without breaking a vacuum, without interruption as a timeline, without changing treatment conditions, or immediately thereafter. In some embodiments, the method further comprises applying RF power to the reaction space between steps (i) and (ii). In some embodiments, the reactant is supplied only during step (iii), and RF power is applied in step (iii). In some embodiments, the method further comprises applying RF power to the reaction space between steps (i) and (ii).

In some embodiments, a rare gas is continuously supplied to the reaction space throughout steps (i) to (iii). In some embodiments, the method further comprises purging the reaction space between steps (i) and (ii), between steps (ii) and (iii), and between steps (iii) and (i).

In some embodiments, the method further comprises, after step (iv), (v) exposing the film on the substrate to a plasma of an inert gas, a hydrogen-containing gas, ammonium-containing gas, and/or oxidizing gas.

In some embodiments, a conformality of the film formed in the recess is 95% or higher.

Steps (i) to (iv) and optionally (v) can be performed using any suitable apparatus. For example, FIG. 6 is a schematic view of an apparatus combining a plasma-enhanced ALD reactor and flow control valves, desirably in conjunction with controls programmed to conduct the sequences described below, which can be used in an embodiment of the present invention. In this figure, by providing a pair of electrically conductive flat-plate electrodes 44, 42 in parallel and facing each other in the interior 51 of a reaction chamber 43, applying HRF power (13.56 MHz or 27 MHz) 45 (and LRF power of 5 MHz or less (400 kHz-500 kHz) 90 as necessary) to one side, and electrically grounding 52 the other side, a plasma is excited between the electrodes. A temperature regulator is provided in a lower stage 42 (the lower electrode), and a temperature of a substrate 41 placed thereon is kept constant at a given temperature. The upper electrode 44 serves as a showerhead as well, and process gas and other gases are introduced into the reaction chamber 43. A first precursor is provided to the showerhead 44 through a gas flow controller 63 and pulse flow control valves 71-73. The precursor is stored as a liquid in a bottle 74 equipped with a heater. A rare gas as a carrier gas can continuously flow into the reaction chamber 43 either (a) through the valve 71 when the valves 72 and 73 are closed, or (b) through the valve 72, the bottle 74, and the valve 73 when the valve 71 is closed. In (b), the rare gas carries the precursor and flows into the reaction chamber 43 together with the precursor. In (a), the rare gas alone flows into the reaction chamber 43 without the precursor. By the above mechanism with operation of the valves, the rare gas can be fed continuously while pulsing the feed of the precursor. This system is referred to as a flow pass system (FPS). A second precursor stored in a bottle 78 can be provided to the showerhead 44 in the same manner as the first precursor using a gas flow controller 65 and pulse flow control valves 75-77. When the precursor has a low vapor pressure, by heating the gas lines of the FPS and/or the bottle with a heater (not shown), the vapor pressure of the precursor can be increased, thereby increasing the supply amount to the reaction space. In some embodiments, in place of the FPS, an automatic pressure regulator (APR) can be used for feeding the precursor gas wherein a carrier gas flows only together with a precursor. A reactant gas can be provided to the showerhead 44 through a gas flow controller 61, and a dilution gas can be provided to the showerhead 44 through a gas flow controller 62. Additionally, in the reaction chamber 43, an exhaust pipe 46 is provided, through which gas in the interior 51 of the reaction chamber 43 is exhausted. Additionally, the reaction chamber is provided with a seal gas flow controller 64 to introduce seal gas into the interior 51 of the reaction chamber 43 (a separation plate for separating a reaction zone and a transfer zone in the interior of the reaction chamber is omitted from this figure).

A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) are communicated with the various power sources, heating systems, pumps, robotics and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

Steps (i) to (iv) can be performed in various sequences as illustrated in FIGS. 2 to 5, for example. FIG. 1 shows a schematic process sequence of PEALD in one cycle according to a comparative example wherein a step illustrated in a column represents an ON state whereas no step illustrated in a column represents an OFF state, and the width of each column does not represent duration of each process. FIGS. 2 to 5 show schematic process sequences of PEALD in one cycle according to embodiments of the present invention wherein a step illustrated in a column represents an ON state whereas no step illustrated in a column represents an OFF state, and the width of each column does not represent duration of each process.

In FIG. 1, no second precursor is used, and a reactant, carrier gas, and dilution gas continuously flow. These gases function as a purge gas before and after a first precursor is introduced in each cycle. That is, after adsorbing the first precursor on a substrate, non-adsorbed components are removed from the surface of the substrate using the purge gas, and then RF power is applied to the reaction space so that the first-precursor adsorbed surface is exposed to a plasma of the reactant, thereby fixing a monolayer or sub-layer (or atomic layer) which will constitute a film on the substrate. Thereafter, non-reacted components are removed from the monolayer of the substrate using the purge gas. The above one cycle is repeated to form a film on the substrate.

In FIG. 2, the process sequence is similar to that illustrated in FIG. 1, except that a second precursor which contains no silicon or metal in its molecule is introduced after a first precursor which contains silicon or metal in its molecule. Purging is conducted after adsorbing the first precursor but before adsorbing the second precursor, and after adsorbing the second precursor but before applying RF power, and after applying RF power but before adsorbing the first precursor. By the above sequence, Si—O—X, Si—N—X, or Si—C—X (X is an element other than silicon or metal) bonds are formed after adsorbing the Si/metal-free second precursor on top of the Si/metal-containing first precursor adsorbed on the substrate surface, prior to activation of the adsorbed precursors by an excited reactant, so that activation of the adsorbed precursors can significantly be promoted, and densification can be performed. For example, when dichloromethylsilane is used as the first precursor and chemisorbed on a surface of a substrate, and then diethylamine is adsorbed as the second precursor, followed by applying about 100 W of RF power of 13.56 MHz for one second while supplying H₂ and N₂ each at about 1 SLM, it has been confirmed that a SiN film having a step coverage of about 90% can be formed on the substrate. It has been confirmed that if diethylamine is not used, a film obtained is a SiN film having a step coverage of about 80% and containing a small amount of carbon. Thus, it has been confirmed that a combination of a Si-containing precursor and a Si-free amine-containing precursor which are alternately adsorbed can improve nitridization of a side film. Alternate adsorption of a Si-containing precursor and a Si-free amine-containing precursor can also increase reflective index (RI) by about 0.05 to 0.1, as compared with the use of a Si-containing precursor without a Si-free amine-containing precursor. By selecting a suitable second precursor and a suitable reactant, not only nitridization, but also oxidization or carbonization of the precursors can be promoted.

In FIG. 3, the process sequence is similar to that illustrated in FIG. 2, except that RF power is applied also before adsorbing the second precursor. The adsorbed first precursor is activated by an excited reactant before adsorbing the second precursor, and then, the adsorbed second precursor is activated by an excited reactant. In the sequence illustrated in FIG. 2, nitridization/oxidization/carbonization of the precursors is performed after alternately adsorbing the precursors, whereas in the sequence illustrated in FIG. 3, RF power is applied after adsorbing the first precursor to conduct nitridization/oxidization/carbonization of the first precursor so that the second precursor can more easily be adsorbed and also, improvement of film quality of a side wall film is expected. The same combinations of the precursors and the reactant gas can be employed in the sequences illustrated in FIGS. 2 and 3. In the process sequence illustrated in FIG. 3, no purge is conducted after applying RF power before supplying the second precursor, so that interaction between the first and second precursors can be maintained while densifying each monolayer. In the sequences illustrated in FIGS. 2 and 3, the reactant gas is supplied continuously to the reaction space. This is because the reactant and the precursors do not cause reaction merely by mixing them together in the reaction space. For example, a precursor other than halide having two or more halogen groups, and a reactant other than O₂ or N—H gas such as NH₃, can be supplied in accordance with the sequence illustrated in FIG. 2 or 3.

In FIG. 4, the process sequence is similar to that illustrated in FIG. 2, except that the reactant is not continuously introduced to the reaction space, but is introduced in a pulse beginning after introducing the Si-free precursor and purging the reaction space but before applying RF power to the reaction space, and ending when RF power application ends. This sequence is effective when the precursors and the reactant are reactive to each other without excitation. For example, a precursor which is a halide and a reactant which is oxygen or ammonium (e.g., for a SiN film) may be reactive to each other. By separating a pulse of the Si precursor, a pulse of the Si-free precursor, and a pulse of the reactant, generation of particles can be suppressed, and safety may be increased (continuous supply of the flammable reactant may require more careful processes). However, pulsing the reactant may decrease productivity or throughput.

In FIG. 5, the process sequence is similar to that illustrated in FIG. 3, except that the reactant is not continuously introduced to the reaction space, but is introduced in a pulse beginning after introducing the Si-free precursor and purging the reaction space but before applying RF power to the reaction space, and ending when RF power application ends. This sequence is effective when the precursors and the reactant are reactive to each other without excitation. For example, a precursor which is a halide and a reactant which is oxygen or ammonium may be reactive to each other. By separating a pulse of the Si precursor, a pulse of the Si-free precursor, and a pulse of the reactant, generation of particles can be suppressed, and safety may be increased (continuous supply of the flammable reactant may require more careful processes). However, pulsing the reactant may decrease productivity or throughput.

When the reactant gas is excited by energy other than in-situ plasma, such as heat or remote plasma, the sequences illustrated in FIGS. 4 and 5 can be modified accordingly, wherein the reactant gas excited by heat or remote plasma is introduced in a pulse as illustrated in FIGS. 4 and 5 without application of RF power.

In some embodiments, more than one reactant gas can be used in sequence. For example, a second reactant can be introduced in a pulse after the pulse of the first reactant gas illustrated in FIG. 4 in a manner substantially similar to that for the first reactant gas. For example, the first reactant gas is ammonia, and the second reactant gas is hydrogen, whereby the refractive index of a resultant film may increase, and wet etch rate thereof may decrease. In some embodiments, no purge time is set after each pulse of gas.

In some embodiments, a conformal dielectric film can be formed by PEALD under conditions shown in Table 1 below, although the conditions may vary depending on the type of film, the type of precursor, the type of reactant, etc. Since ALD is a self-limiting adsorption reaction process, the amount of deposited precursor molecules is determined by the number of reactive surface sites and is independent of the precursor exposure after saturation, and a supply of the precursor is such that the reactive surface sites are saturated thereby per cycle.

TABLE 1 (the numbers are approximate) Typically Preferably (±50%) Quantity of first precursor 0.0001 to 0.01 g/cycle 0.0005 g/cycle Quantity of second precursor 0.0005 to 0.01 g/cycle 0.003 g/cycle Carrier gas flow for each first and 1000 sccm to 3000 2000 sccm second precursors (continuous) sccm Reactant gas flow (continuous) 200 sccm to 5000 2000 sccm sccm Dilution gas flow (continuous) 200 sccm to 5000 2000 sccm sccm Substrate temperature 25° C. to 650° C. 300° C. Pressure 133 Pa to 800 Pa 400 Pa RF power (13.56 MHz) 10 W to 1000 W 200 W (300-mm tool) Step First percursor supply time 0.05 sec. to 4 sec. 0.2 sec. (i) Purge time after precursor 0.2 sec. to 3 sec. 0.3 sec. pulse Step Second precursor supply time 0.05 sec.to 4 sec. 0.2 sec. (ii) Purge time after precursor 0.2 sec. to 3 sec. 0.3 sec. pulse Step RF plasma exciting time 0.05 sec. to 5 sec. 0.2 sec. (iii) Purge time after RF 0.05 sec. to 1 sec. 0.1 sec. application Number of cycles 10-200 50

In the above, by continuously feeding the carrier gas and the dilution gas, no separate purge gas is required, since the continuous feed of these gases functions as a mechanism of purging. The reactant gas can be continuously fed since it is not reactive to the precursor, and thus, the continuous feed of the reactant gas also functions as a mechanism of purging.

In some embodiments, the thickness of the oxide film by PEALD is in a range of about 1 nm to about 350 nm (a desired film thickness can be selected as deemed appropriate according to the application and purpose of film, etc.).

As a carrier gas, seal gas, purge gas, or process-adjustment gas (dilution or auxiliary gas), a rare gas such as Ar, He, Ne, Kr, and Xe can be used, singly or in any combination of two or more.

In some embodiments, after the film formation process, a plasma of a rare gas, hydrogen-containing gas, ammonia-containing gas, and/or oxidization gas is applied to the film as a post-film formation process. The post-film formation process can be conducted continuously in the same reaction chamber upon the film formation process. The post-film formation process can be conducted under conditions as shown in Table 2 below (as for a 300-mm substrate).

TABLE 2 Gas O₂, O₃, NH₃, H₂, N₂, Ar, and/or He Gas flow 100 to 8000 sccm (typically 1000 to 4000 sccm) Susceptor Temperature 50 to 420° C. (typically 200 to 400° C.) RF power 50 to 1000 W (typically 50 to 400 W) (13.56 MHz) Pressure 133 to 1333 Pa (typically 266 to 533 Pa) Duration 10 to 300 seconds (typically 30 to 60 seconds)

The embodiments will be explained with respect to preferred embodiments. However, the present invention is not limited to the preferred embodiments

EXAMPLES

In the following examples where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation.

A dielectric film was deposited on a bare silicon substrate (Φ300 mm) by PEALD under common conditions shown in Table 2 below using the PEALD apparatus illustrated in FIG. 6. The specific conditions including the process sequence (SQ) are shown in Table 3. The flow rate of the precursor (g/cycle) was calculated based on the vapor pressure of the precursor and the temperature of the precursor in use. The SQ number corresponds to the figure number. The substrate had a flat surface and trenches having an opening width of about 40 nm and an aspect ratio of 1:7.5. The thickness of film was 350 nm for evaluating film properties.

TABLE 2 Carrier gas Ar; 2 SLM Dilution gas 100-2000 sccm Susceptor Temperature 300° C. Distance between electrodes 13 mm RF power 13.56 MHz

TABLE 3 SQ Flow Si/metal-free Flow Reactant Pressure RF FIG. Ex. Si/metal precursor (g/Cycle) precursor (g/Cycle) (SLM) (Pa) (W) # C1 Dichlorodimethylsilane 0.01 — — NH3 400 200 1 (2) C2 Dichlorotetraethyldisilane 0.005 — — NH3 400 200 1 (2) C3 Dis(diethylamino)silane 0.005 — — O2 200 100 1 (0.5) C4 Diethylaluminium- 0.001 — — O2 200 50 1 isopropoxide (0.1) 1 Dichlorodiethylsilane 0.01 Diethylamine 0.02 NH3 400 200 2 (2) 2 Dichlorodiethylsilane 0.01 Diethylamine 0.02 NH3 400 200 3 (2) 3 Dichlorodimethylsilane 0.007 Diethylamine 0.02 NH3 400 200 2 (2) 4 Dichlorodimethylsilane 0.007 Diethylamine 0.02 NH3 400 200 3 (2) 5 Dichlorodiethylsilane 0.01 Diethylether 0.01 O2 400 200 2 (0.1) 6 Dichlorodiethylsilane 0.01 Diethylether 0.01 O2 400 200 3 (0.1) 7 Dichlorotetraethyldisilane 0.005 Diethylamine 0.02 NH3 400 400 2 (2) 8 Dichlorotetraethyldisilane 0.005 Diethylamine 0.03 NH3 400 400 2 (2) 9 Dichloroethylsilane 0.02 Diethylamine 0.02 NH3 400 400 2 (2) 10  Dichloroethylsilane 0.02 Diethylamine 0.03 NH3 400 400 2 (2) 11  Dis(diethylamino)silane 0.005 Diethylether 0.05 O2 200 100 3 (0.1) 12  Diethylaluminium- 0.001 Diethylether 0.05 O2 200 50 4 isopropoxide (0.1)

The film was analyzed in terms of growth rate per cycle (GPC) (nm/cycle), refractive index (RI) at 635 nm, side step coverage (ratio in percentage of thickness of film on sidewall to thickness of film on top surface), bottom step coverage (ratio in percentage of thickness of film on bottom surface to thickness of film on top surface), ratio of wet etch rate (WERR) of the film on flat surface in DHF (100:1) to that of thermal oxide film on flat surface, and ratio of wet etch rate (WERR) of the film on sidewall in DHF (100:1) to that of the film on top surface. Results are shown in Table 4 below.

TABLE 4 100:1 DHF 100:1 DHF Step Step WERR WERR GPC coverage coverage Relative to Relative to [nm/ RI@ (side) (bottom) thermal film on Ex cycle] 633 nm [%] [%] oxide film pattern top C1 0.03 1.71 80 80 5 >10 C2 0.03 1.71 80 80 5 >10 C3 0.1  1.46 95 95 1 1.4 C4 0.1  1.65 95 95 8.5 1.5 1 0.04 1.84 95 96 0.5 1 2 0.06 1.85 97 96 0.5 1 3 0.05 1.82 97 99 0.6 1.1 4 0.05 1.86 97 96 0.8 0.8 5 0.1  1.45 97 98 1.1 1.2 6 0.1  1.47 97 93 1.2 0.9 7 0.06 1.89 98 98 0.6 0.8 8 0.07 1.90 97 99 0.6 0.8 9 0.05 1.84 96 97 0.9 1.4 10  0.06 1.83 99 95 0.9 1.2 11  0.13 1.45 95 95 0.7 1.0 12  0.13 1.67 95 95 2.6 0.8

As shown in Table 4, when using a silicon-containing halide precursor as a first precursor without a second precursor in Examples C1 and C2 to form a nitride film, the step coverage at the side and the bottom was relatively low (80%), and the wet etch rate of the film on a flat surface was significantly higher than that of thermal oxide film, and the wet etch rate of the film on the sidewall was significantly higher than that of the film on the top surface. In contrast, when using the silicon-containing halide precursor as a first precursor with an amine compound as a second precursor in Examples 1, 2, 7, and 8 to form a nitride film, the step coverage at the side and the bottom was high (at least 95%), and the wet etch rate of the film on a flat surface was significantly lower than that of thermal oxide film, and the wet etch rate of the film on the sidewall was equal to or substantially equal to that of the film on the top surface. Further, the refractive index of the film in Examples 1, 2, 7, and 8 was significantly higher than that in Example C1 and C2. That is, by using the second precursor, surprisingly uniform and conformal films with good film quality can be formed. Further, when RF power was applied after each pulse of the first and second precursors in Example 2, slight improvements on growth rate, refractive index, and side step coverage were observed as compared with those in Example 1. Additionally, when the second precursor was supplied in amounts 6 times higher than the first precursor in Example 8, slight improvements on growth rate, refractive index, and the step coverage at the bottom were observed as compared with those in Example 7 (wherein the second precursor was supplied in amounts 4 times higher than the first precursor).

When using an aminosilane precursor as a first precursor without a second precursor in Example C3 to form an oxide film, although the step coverage at the side and the bottom were relatively high, the wet etch rate of the film on the sidewall was significantly higher than that of the film on the top surface. In contrast, when using an aminosilane precursor as a first precursor with an ether compound as a second precursor in Example 11 to form an oxide film, the wet etch rate of the film on the sidewall was equal to that of the film on the top surface, indicating that film densification on the sidewall was more progressed than at the bottom. Further, the wet etch rate in Example 11 was lower than that in Example C3, and the growth rate in Example 11 was also higher than that in Example C3.

When using a metal oxide precursor as a first precursor without a second precursor in Example C4 to form an oxide film, although the step coverage at the side and the bottom was relatively high, the wet etch rate of the film on the sidewall was significantly higher than that of the film on the top surface. In contrast, when using a metal oxide precursor as a first precursor with an ether compound as a second precursor in Example 12 to form an oxide film, the wet etch rate of the film on the sidewall was equal to that of the film on the top surface. Further, the wet etch rate in Example 12 was lower than that in Example C4, and the growth rate in Example 12 was also higher than that in Example C4.

When using dichlorodimethylsilane as a first precursor in Examples 3 and 4 in place of dichlorodiethylsilane in Examples 1 and 2, the resultant film had uniformity, conformality, and quality equivalent to those in Examples 1 and 2. When using an silicon-containing halide precursor as a first precursor in Examples 5 and 6 in place of the aminosilane precursor in Example 11, the resultant film had uniformity, conformality, and quality nearly equivalent to those in Example 11, except that the wet etch rate in Examples 5 and 6 was higher than that in Example 11.

When using dichloroethylsilane as a first precursor in Example 9 in place of dichlorodiethylsilane in Example 1, the wet etch rate of the film on a flat surface was higher than that in Example 1, and the wet etch rate of the film on the sidewall was higher than that of the film on the top surface. Additionally, when the second precursor was supplied in amounts 1.5 times higher than the first precursor in Example 10, slight improvements on growth rate, refractive index, and the wet etch rate step coverage at the sidewall were observed as compared with those in Example 9 (wherein the second precursor was supplied in amounts equal to the first precursor).

Additionally, when RF power was applied after each pulse of the first and second precursors in Examples 4 and 6, slight improvements on film densification on the sidewall were observed as compared with densification in Examples 3 and 5, respectively. Further, in comparing Examples 1, 3, and 9, the use of the “diethyl” first precursor in Example 1 exhibited better and more even film densification than the use of the “dimethyl” first precursor in Example 3, or the use of the “ethyl” first precursor in Example 9.

Table 5 below shows the results of composition analysis of the films by Rutherford backscattering/hydrogen forward scattering (RBS/HFS).

TABLE 5 Example Si (atm %) N (atm %) C (atm %) H (atm %) C1 35 37 3 25 1 35 49 N/D 16 C2 35 41 3 21 7 37 52 N/D 11

As shown in Table 5, by using the second precursor which does not contain silicon or metal, nitridization of the films progressed, thereby reducing the carbon content.

It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention. 

I claim:
 1. A method for forming a film on a patterned surface of a substrate by atomic layer deposition (ALD) processing, said surface being patterned with a recess having side walls and a bottom, said ALD processing being constituted by a plurality of atomic layer deposition cycles, each cycle comprising in the following sequence of steps (i) to (iii) using a first precursor containing silicon in its molecule, a second precursor containing no silicon in its molecule, and a reactant for nitriding the precursors, said reactant being neither first nor second precursor, being nitriding gas selected from the group consisting of NH₃, N_(x)H_(y), and N_(x)H_(y)C_(z) (x, y, and z are integers) excluding N₂, and having a smaller molecular size than the second precursor, each cycle being defined as a cycle forming a monolayer using the first precursor and a monolayer using the second precursor, wherein the reactant is continuously supplied to the reaction space throughout steps (i) to (iii): (i) adsorbing a non-excited gas of the first precursor onto a patterned surface of a substrate in a reaction space by feeding the first precursor to the reaction space in a pulse; (ia) purging the reaction space between steps (i) and (ib) to purge therefrom the first precursor present in the reaction space; (ib) applying RF power to the reaction space between steps (ia) and (ii) to excite the reactant to conduct nitridization of the first precursor; (ii) adsorbing a non-excited gas of the second precursor onto the first-precursor-adsorbed surface of the substrate in the reaction space by feeding the second precursor to the reaction space in a pulse so as to form Si—N—X (X represents an element other than silicon and metal in the second precursor); (iia) purging the reaction space between steps (ii) and (iii) to purge therefrom the second precursor present in the reaction space where the first precursor is already purged; (iii) applying RF power to the reaction space between steps (iia) and (iv) to expose the non-excited second-precursor-adsorbed surface of the substrate to an excited gas of the reactant to nitride the precursors adsorbed on the surface of the substrate; said ALD processing further comprising (iv) repeating the cycle constituted by steps (i) to (iii) to form a film on the patterned surface of the substrate, step (iv) further comprising purging the reaction space between steps (iii) and (i) when repeating the cycle.
 2. The method according to claim 1, wherein the second precursor is at least one compound selected from the group consisting of C_(x)N_(y)H_(z) and N_(x)H_(y) (x, y, and z are integers), whereby the excited reactant nitrides the precursors adsorbed on the surface of the substrate.
 3. The method according to claim 1, wherein the first precursor is at least one selected from the group consisting of dichlorodiethylsilane, dichlorodimethylsilane, dichlorotetramethyldisilazane, dichlorotetraethyldisilazane, dichloroethylsilane, dichloromethylsilane, diiodomethylsilane, diiodoethylsilane.
 4. The method according to claim 1, wherein the first precursor is an aminosilane compound.
 5. The method according to claim 4, wherein the first precursor is at least one selected from the group consisting of bis(diethylamino)silane and bis(dimethylamino)silane.
 6. The method according to claim 1, wherein the first and second precursors are organic compounds which are liquid at room temperature.
 7. The method according to claim 1, wherein the adsorbed weight of the second precursor in step (ii) is equivalent to or higher than the adsorbed weight of the first precursor in step (i).
 8. The method according to claim 1, wherein the reactant is excited by heat and/or a plasma in step (iii).
 9. The method according to claim 8, wherein the reactant is excited by a plasma generated by applying RF power to the reaction space.
 10. The method according to claim 1, further comprising, after step (iv), (v) exposing the film on the substrate to a plasma of an inert gas, a hydrogen-containing gas, ammonium-containing gas, and/or oxidizing gas.
 11. The method according to claim 1, wherein no purge is conducted between steps (ib) and (ii). 